This application claims the benefit of Korean Application No. 98-49073, filed Nov. 16, 1998, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for jetting fluid, and method of manufacturing the same, and more particularly to a fluid jetting apparatus of a print head employed in output apparatuses such as an ink jet printer, a facsimile machine, etc., to jet fluid through a nozzle.
2. Description of the Related Art
A print head is a part or a set of parts which are capable of converting output data into a visible form on a predetermined medium using a type of printer. Generally, such a print head for an ink jet printer and the like, uses a fluid jetting apparatus which is capable of jetting a predetermined amount of fluid through a nozzle to an exterior of the ink jet printer or related device by applying a physical force to a fluid chamber holding the fluid.
According to a method for applying a physical force to the fluid within the fluid chamber, a fluid jetting apparatus is roughly grouped into a piezoelectric system and a thermal system. The piezoelectric system pushes the fluid within a fluid chamber through the nozzle by an operation of a piezoelectric element which is mechanically expanded in accordance with a driving signal. The thermal system pushes the fluid through the nozzle by bubbles which are produced in the fluid within a fluid chamber due to heat generated by an exothermic body. Recently, also, a thermal compression system has been developed, which is an improved form of the thermal system. The thermal compression system jets the fluid by driving a membrane by instantly heating a vaporizing fluid which acts as a working fluid.
FIG. 1 is a vertical sectional view of a fluid jetting apparatus according to a conventional thermal compression system. A fluid jetting apparatus of the thermal compression system includes a heat driving part 10, a membrane 20, and a nozzle part 30. Referring to the heat driving part 10, a reference numeral 11 is a silicon substrate, 12 is a nonconductive layer, 13 is an exothermic body, and 14 is an electrode. The reference numeral 15 is a barrier layer for a working fluid, 16 and 17 are working fluid chambers, and 18 is a passage for introduction of the working fluid.
Referring to the membrane 20, a reference numeral 21 is a polyimide coated layer, and 22 is a polyimide adhered layer.
Referring to the nozzle part 30, a reference numeral 34 is a nozzle plate, 35 is a nozzle, 36 is a barrier layer of jetting fluid. Reference numerals 37 and 38 are jetting fluid chambers, and 39 is a passage for introduction of the jetting fluid.
The substrate 11 of the heat driving part 10 supports the heat driving part 10 and the whole, complete, structure that will be constructed later. The electrode 14 is a conductive material for supplying an electric power for the heat driving part 10. The exothermic body 13 is a resistive material having a predetermined resistance for expanding a working fluid by converting electrical energy into thermal energy. The working fluid chambers 16 and 17 contain the working fluid, to maintain the pressure of the working fluid which is expanded by the heat.
Further, the membrane 20 is a thin layer which is adhered to an upper portion of the working fluid chambers 16 and 17, and is moved upward and downward by the pressure of the expanded working fluid. The membrane 20 includes a polyimide coated layer 21 and a polyimide adhered layer 22.
The jetting fluid chambers 37 and 38 are formed in a jetting fluid barrier layer 3b to contain the jetting fluid, and designed to jet the fluid only through a nozzle 35 when the pressure transmitted through the membrane 20 is applied to the jetting fluid. Here, the jetting fluid is the fluid which is pushed out of the jetting fluid chambers 37 (through the nozzle 35) and 38 (via the jetting passage 39) in response to the driving of the membrane 20, and finally jetted to the exterior. The nozzle 35 is an orifice through which the jetting fluid held within the jetting fluid chambers 37 and 38 is emitted to the exterior. A substrate (not shown) of the nozzle part 30 is temporarily employed for constructing the nozzle part 30, and the substrate of the nozzle part 30 should be separated before the nozzle part 30 is assembled.
A process of manufacturing the fluid jetting apparatus according to the conventional thermal compression system will be described below.
FIGS. 2A to 2C are views for showing a process of manufacturing the heat driving part 10 and the membrane 20 of the fluid jetting apparatus of the prior art. FIGS. 3A to 3C are views for showing a process for manufacturing the nozzle part 30.
In order to manufacture the conventional fluid jetting apparatus, the heat driving part 10 and the nozzle part 30 should be separately manufactured. Here, the heat driving part 10 is completed and the separately-made membrane 20 is adhered to the substrate 11 of the heat driving part 10. After that, by reversing and adhering the separately-made nozzle part 30, the fluid jetting apparatus is completed.
FIG. 2A shows a sequential process of diffusing the insulated (non-conductive) layer 12 on the substrate 11 of the heat driving part 10, for forming the exothermic body 13 and the electrode 14 thereon. FIG. 2B shows a process of performing an etching process through a predetermined mask patterning to make the working fluid chambers 16 and 17 and the passage 18 for introduction of the working fluid. More specifically, the heat driving part 10 is formed as the insulated layer 12, the exothermic body 13, the electrode 14, and the barrier layer 15 for the working fluid are sequentially laminated on the upper portion of the silicon substrate 11. In such a situation, the working fluid chambers 16 and 17, formed on the etched portion of the working fluid barrier layer 15, are filled with the working fluid to be expanded by heat. The working fluid is introduced through the passage 18 for introduction of the working fluid.
FIG. 2C shows a process of adhering the separately-made membrane 20 to the upper portion of the completed heat driving part 10. The membrane 20 is a thin diaphragm, which is to be driven toward a direction of the jetting fluid chamber 37 by the working fluid which is heated by the exothermic body 13.
FIG. 3A shows a process of forming an insulated layer 32 and the nozzle plate 34 on the upper portion of the substrate 31 of the nozzle part 30, and then forming the nozzle 35 by a laser processing equipment (not shown). FIG. 3B shows a sequential process of forming the jetting fluid barrier layer 36 on the upper portion of the construction shown in FIG. 3A, of forming the jetting fluid chambers 37 and 38 and the fluid introducing passage 39 by an etching process through a predetermined mask patterning. FIG. 3C shows a process of exclusively separating the nozzle part 10 from the substrate 31 of the nozzle part 30. The nozzle part 30 includes the jetting fluid barrier layer 36 and the nozzle plate 34. On the etched portion of the jetting fluid barrier layer 36, the jetting fluid chambers 37 and 38 to be filled with the jetting fluid, are formed. The jetting fluid such as ink and the like is introduced through the jetting fluid introducing passage 39. The nozzle 35 is formed on the nozzle plate 34 to be interconnected with the jetting fluid chamber 37, so that the jetting fluid is jetted through the nozzle 35.
The operation of the fluid jetting apparatus according to the thermal compressions system will be described with reference to the above-mentioned FIG. 1.
First, an electric power is supplied through the electrode 14, and electric current flows through the exothermic body 13 which is connected to the electrode 14. In such a situation, the exothermic body 13 generates heat due to its resistance. The working fluid within the working fluid chamber 16 is subjected to a resistance heating, so that the working fluid starts to vaporize when the temperature thereof exceeds a predetermined degree. As the amount of the working fluid vaporized by the heat increases, the vapor pressure increases. As a result, the membrane 20 is driven upward. More specifically, as the working fluid undergoes the thermal expansion, the membrane 20 is pushed upward in a direction indicated by the arrow in FIG. 1. As the membrane 20 is pushed upward, the jetting fluid within the jetting fluid chamber 37 is jetted to the exterior through the nozzle 35.
Then, when the supply of the electric power is stopped, the resistance heating is no longer generated out of the exothermic body 13. Accordingly, the working fluid within the working fluid chamber 16 is cooled to a liquid state, so that the volume thereof decreases and the membrane 20 recovers its original shape.
Meanwhile, a conventional material used for the nozzle plate 34 is mainly nickel, but the trend in using a material of a polyimide synthetic resin has increased recently. When the nozzle plate 34 is made of the polyimide synthetic resin, it is fed by a reel type. The fluid jetting apparatus is completed by the way a chip laminated from the silicon substrate 11 to the jetting fluid barrier layer 36 is bonded on the nozzle plate 34 in the reel type.
The conventional fluid jetting apparatuses, however, have the following drawbacks.
First, since a piezoelectric element is expensive, the fluid jetting apparatus becomes expensive if the same employs the piezoelectric element. Second, if the fluid jetting apparatus employs a thermal system, or a thermal compression system, then the responsive quality thereof can not be guaranteed due to its mechanism in which the working fluid is heated, vaporized, and then thermally expanded, to generate a pressure for exerting the physical force to the fluid. More specifically, since the working fluid should be heated and then vaporized to generate the pressure for driving the membrane, the responsive quality of the fluid jetting apparatus deteriorates.
Third, if the fluid jetting apparatus employs the thermal compression system, a precision process of forming the working fluid introducing passage, and also, the process of introducing the working fluid into the working fluid chamber, are required. This causes productivity to be decreased. Finally, due to the high vapor pressure which is produced while heating the working fluid, leakage may occur between the working fluid chamber and the membrane, or between the working fluid chamber and the substrate, so that the reliability of the fuel jetting apparatus deteriorates.
The present invention has been made to overcome the above-described problems of the related art, and accordingly it is a first object of the present invention to provide an apparatus for jetting fluid which employs an electrostatic force and has a greater responsiveness than a fluid jetting apparatus according to a thermal system or a thermal compression system.
A second object of the present invention is to provide an apparatus for jetting fluid which employs an electrostatic force for jetting fluid regardless of the property of the fluid by driving an organic membrane with an electrostatic attraction.
In order to accomplish the first object, the present invention provides an apparatus for jetting fluid comprising a lower electrode, a membrane, a jetting fluid chamber which contains the fluid, a nozzle, and means including the membrane and the lower electrode, for exerting a driving force to the fluid within the jetting fluid chamber by generating an electrostatic force between the membrane and the lower electrode so as to jet a predetermined amount of the fluid outside of the nozzle.
Here, the exerting means further includes an upper electrode so that the upper electrode and the lower electrode are oppositely spaced apart from each other by a predetermined distance. It is preferable that the exerting means exerts the driving force to the fluid within the jetting fluid chamber by the displacement of the upper electrode upward and downward due to the electrostatic force generated between the upper and lower electrodes.
It is preferable that the upper electrode is disposed in an interior of the membrane to exert the driving force to the fluid within the jetting fluid chamber by driving the membrane.
The membrane has a lower membrane and an electrically conducting metallic layer is formed on the upper surface of the lower membrane. Further, it is preferable that the electrically conductive metallic layer is inserted into the membrane, while being disposed between the lower membrane and an upper membrane, to maintain a secure bond of the metallic layer with the upper and lower membranes which are organic layers.
Also, the metallic layer comprises an upper electrode in the form of a plate, and at least two springs.
It is still preferable that the upper electrode is supported by the membrane and is applied with the electric power through the at least two springs which are shaped to have less stiffness than if the springs are totally straight.
Here, the exerting means further includes a space layer for maintaining a gap defined between the upper and lower electrodes.
In order to accomplish the second object, a fluid jetting apparatus for employing an electrostatic force according to the present invention includes a jetting fluid chamber with a nozzle and a lower surface comprising a membrane, and in which the fluid is accommodated; a lower electrode disposed at a lower side of the membrane; a space layer to maintain a gap between the membrane and the lower electrode; and an upper electrode disposed within the membrane, to drive the membrane by the electrostatic force generated between the lower electrode and the upper electrode in response to the electric power being applied thereto so as to jet the fluid through the nozzle.
The apparatus for jetting fluid by the electrostatic force according to the present invention, employs the electrostatic force as a driving force exerted to the fluid. The driving force is exerted to the fluid by the upper and lower electrodes which are oppositely spaced apart from each other by a predetermined distance. The upper electrode is disposed within the membrane which forms the lower surface of the jetting fluid chamber. Accordingly, the membrane is driven by the upper electrode which is displaced upward and downward due to the electrostatic force generated between the upper and lower electrodes, so that the driving force is exerted on the fluid within the jetting fluid chamber and the fluid is jetted out through the nozzle.